In outline, such an insulator consists of a rod made of resin and glass fibre covered with an elastomer sheath which may be fitted with fins also made of an elastomer e.g. EPDM (Ethylene-Propylene-Diene Monomer). One of its ends is fixed to a post by means of a fitting and the other end has another fitting to which a clip for a conductor is attached.
The rod as a whole and in particular its end which is anchored in the fitting fixed to the post is subject to great mechanical stress. It tends to sag under the weight of the conductor; the upper fibres are subject to a traction force while the lower fibres are subject to a compression force.
To improve the anchoring of the end of the rod, it has already been proposed to machine said end so as to impart a cone or double cone shape thereto; however, under the effect of high mechanical loading it has been observed that cracks appear between the fibres parallel to the direction thereof.
Preferred embodiments of the present invention mitigate this drawback and provide an insulator of the line post type which has anchoring means at its end nearest to the post conferring improved mechanical strength to the rod.